A communication device may communicate with another communication device. For example in order to enhance security of one or both of the communication devices, data exchanged between the communication devices may be routed via a flow restriction device, for example a firewall. The flow restricting device may decide whether to block the data exchange or to allow the data exchange. However, it may be cumbersome for a user of the communication device in case data exchange is blocked. Thus, there is the need for a communication system with a flow restricting device that does not filter any data that should not be filtered.